We have investigated the growth of GaAsBi single-crystal film on Ge substrate by gas source molecular beam epitaxy. A high-quality GaAsBi epilayer has been obtained. It has been found that the surfactant effect of Bi suppresses the interdiffusion of Ge at the GaAsBi/Ge interface and reduces the misfit dislocation density. The Bi atoms occupy the As sites, as indicated by the appearance of GaBi-like TO(Γ) and LO(Γ) phonon modes in Raman spectra. In addition, the redshift of the GaAs-like LO(Γ) phonon frequency has been observed in the Raman spectra, owing to the Bi-induced biaxial strain and the alloying effect as well.